1. Field of the Invention
The present invention relates to a construction machine having a vertical separating/connecting device for separating a lower traveling body and an upper rotating body from each other and connecting the lower traveling body and the upper rotating body to each other.
2. Description of the Related Art
When a large mobile crane runs on a public road, the mobile crane must be disassembled into a lower traveling body and an upper rotating body at a swing bearing in order to comply with the weight limit as an automobile. However, since the weight limits of automobiles differ depending on the regulations of each country, the necessity of separating cranes differs depending on the country in which they are used even when the cranes are of the same model. This also applies to the case in which crawler cranes are transported by trailers. Accordingly, the following problems occur when cranes with the same specification are exported to different countries over the world.
That is, if a crane is provided with a vertical separating/connecting device even though it is not necessary to separate the crane into a lower traveling body and an upper rotating body when the crane runs or is transported on a public road, the cost is increased by the amount corresponding to the cost of the vertical separating/connecting device and the height of the device is also increased. In addition, if two types of cranes, i.e., cranes having the above-mentioned device and cranes free from the above-mentioned device, are manufactured, compatibility cannot be achieved between lower traveling bodies and upper rotating bodies of the two types of cranes. Accordingly, the development cost and the management cost are increased.
Japanese Unexamined Patent Application Publication No. 8-259178 discloses a known mobile crane having a releasable coupling that connects a lower carriage and an upper carriage to each other. An inner race of a swing bearing is fixed to the bottom surface of the upper carriage and an outer race (externally toothed ring) of the swing bearing is fitted around the inner race with rollers arranged in two vertically arranged rows interposed therebetween. The outer race has teeth that mesh with teeth of a pinion rotated by a swing motor along the periphery thereof and a cylindrical extending portion that projects downward from the bottom surface.
The outer race has claw-like ribs that project outward from the outer periphery of the outer race at the bottom end thereof. A holding ring having a ring extension that projects inward from the inner periphery thereof is fixed on the top surface of the lower carriage. The holding ring has claw-like ribs that project inward from the inner periphery of the holding ring at the top end thereof. The claw-like ribs of the holding ring engage with the claw-like ribs of the outer face, and accordingly the coupling establishes or releases connection by maintaining or canceling the engagement between the claw-like ribs.
However, according to this coupling, when, for example, a mobile crane is transported to a certain designation in a disassembled state or when the mobile crane is subjected to periodic inspection or maintenance in a maintenance facility of a dealer or a user, there is a risk that the claw-like ribs that engage with each other cause seizing in the operation of reassembling a lower traveling body and an upper rotating body of the mobile crane. In such a case, the lower traveling body and the upper rotating body cannot be completely separated from each other and the swing bearing must be replaced together with the holding ring. Therefore, assembling cost and maintenance cost of the mobile crane are increased.